Re: [Discuss-gnuradio] 8-bit samples on USRP2 at 33.333Msps

[Josh Blum]

On 11/09/2011 07:07 PM, Marcus D. Leech wrote:
> Just did a quick test of 8-bit samples on a USRP2, on one of my 6-core
> AMD machines.
> 
> I can get to 33Msps with a fairly simple SOURCE-->MULT-->FFT_SINK
> flow-graph, but anything more complicated causes overruns.
> 
> If I try 50Msps, I get near-continuous overruns.
> 
> This is on an AMD Phenom II X6-1055 -- the cores run at 2.8GHz, and I
> have 4GB of 1333MHz memory.
> 
> It's a fairly-wimpy machine as multi-core DSP monsters go, but I thought
> I'd give it a try.
> 

My AMD Athlon(tm) II X4 620 Processor does jyst fine with 50Msps FFT
plotter. Just sayin :-)

> People should be aware that since this uses the upper-half (as far as I
> know) of the ADC, you'll need more gain to drive those
>   8 bits.

There is a configurable scale factor (see the stream args in the grc
block). It defaults to a value that gives you the upper 8.

-Josh